There are numerous types of conventional mechanical padlocks that effectively provide security functions. Each padlock is opened with a key that may be carried separately by one authorized to open the padlock. The key may be common to a number of padlocks. For example, a key carried by a lineman of a power company may provide access to padlocks at a number of power distribution stations. This, however, raises the specter of the power stations becoming accessible to anonymous ne'er-do-wells if this key is lost or duplicated.
The notion of electronic control of padlocks contemplates eliminating such difficulties associated with mechanical padlocks. Despite the prevalence of padlocks, however, and the long-known availability of electronic security systems, no one has heretofore successfully applied electronic security technology to this application, especially for padlocks adapted for extended periods of non-use in outdoor environments.
The security problems with prior art padlocks generally concern their latch mechanisms. Latch mechanisms employing electromagnets are susceptible to magnetic fields, which can be induced by holding magnets close to the lock. A magnetic field of sufficient magnitude can cause the padlock to release. As a result, extra measures such as added shielding must be added to the lock, at added expense.
Padlocks employing solenoid-activated release mechanisms are susceptible to release by applying an impact, such as a hammer blow, to the lock. Solenoid-activated release mechanisms are also susceptible to externally induced magnetic fields.
If left unused for several years in an outdoor environment, electronic padlocks tend to stick, making them unreliable. This is generally due to lack of motive power (whether from a motor, a solenoid, an electromagnet, etc.) sufficient to activate a release mechanism made sluggish by aging of lubricants, ice, foreign matter, etc.
In accordance with a preferred embodiment of the present invention, the foregoing and additional drawbacks of the prior art are overcome. The present invention provides an electronic padlock having a latch assembly operable for releasing and latching the shackle of the padlock. The latch assembly is controlled by a motor or gearmotor that is housed within the lock. The body of the padlock includes contacts so that the power for driving the motor (hence, for releasing the shackle) is applied from an external source, thereby avoiding the unreliability associated with locks that must be left unused for several years in an outdoor environment.
As another aspect of the present invention, the motor is precisely controlled for reliably moving the latch assembly into and out of position for releasing and latching the shackle. To this end, an encoder assembly is provided within the padlock. This assembly includes an encoder element that moves with the motor driven components of the latch assembly. A light emitter/detector pair is mounted inside the padlock body near the encoder element. The output of the light detector varies, depending upon whether the latch assembly, and connected encoder element is in the position for latching the shackle. This output, therefore, is encoder position information that is indicative of whether the shackle is released or latched.
The encoder position information is provided to the a control circuit carried in the padlock. This circuit is also connected to control application of the external power source to the motor. A processor of the circuit correlates the encoder position information with the power control to the motor precisely to move the latch assembly into the latched or released position.
An electronic key provides, in addition to the motor-power supply, information about the identity and authorization level of the key holder. A keypad carried on the key permits an authorized user to signal (request) release of the padlock. The lock control system, as well as that of the key, carries a memory for logging, for example, each lock access by time, key holder duration of lock opening, etc.
As one aspect of the invention, the key also records in memory the last state (open or closed) of a particular padlock. Such information is useful, once extracted from the memory, for checking whether a lock may inadvertently have been left open, without requiring one to return to a remote padlock for a visual check.
The foregoing and additional features and advantages of the present invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.